The Third Generation Partnership Project (3GPP) is working with requirements for providing services on only the Packet-Switched (PS) domain as part of the work on Machine Type Communication (MTC), see, e.g., 3GPP Technical Report (TR) 23.888 V0.5.1, System Improvements for Machine-Type Communications (Release 10) (July 2010). Such services can be called PS-only services or PS-only features.
In the course of that work, draft architectures have been described in 3GPP Temporary Document (Tdoc) S2-115461, Discussions and Conclusions about PS-Only, that was presented at the TSG SA WG2 Meeting #88, San Francisco, Calif., Nov. 14-18, 2011. Those architectures include the following six requirements for PS-only features.
1. PS services and Short Message Service (SMS) for a User Equipment (UE) can be provided through a GSM/EDGE Radio Access Network (GERAN) and a Universal Terrestrial Radio Access Network (UTRAN) without involving a Mobile Switching Center (MSC). This includes the case where a Home Subscriber Server (HSS) does not provide subscription data to a GERAN or UTRAN MSC for that UE when both the UE and its serving Public Land Mobile Network (PLMN) support PS services or SMS.
2. Not receiving services from a GERAN or UTRAN MSC due to a UE's operation with a PS-only feature shall not affect services provided to that UE, which may include that an unsuccessful or rejected registration attempt by a PS-only UE toward a GERAN or UTRAN MSC shall not result in losing SMS provided through another Radio Access Technology (RAT) or domain used by the UE.
3. PS services and SMS can be provided through a Mobile Mobility Entity (MME) of an evolved Universal Terrestrial Radio Access Network (UTRAN) with efficient HSS signaling, which can include an HSS registration procedure that provides subscription data for PS services and SMS together and that should not have adverse effects, such as increased HSS signaling, e.g., when a UE reselects between RATs.
4. The PS-only feature shall not prevent receiving SMS when the UE or its visited or serving PLMN does not provide the capabilities required for the PS-only feature.
5. A UE can be allowed to select one or more appropriate SMS delivery mechanisms. Such mechanisms could use existing E-UTRAN access procedures for SMS via Non-Access Stratum (NAS) signaling (i.e., combined Evolved Packet System/International Mobile Subscriber Identity (EPS/IMSI) Attach and Combined Tracking Area/Location Area (TA/LA) Update) or different procedures (e.g., EPS Attach and TA Update with new information elements). The Serving CPRS Support Node (SGSN) and/or MSC registration procedures in a second-generation (2G) network, such as GERAN, or a third-generation (3G) network, such as UTRAN, could be enhanced to inform the UE that it should use only the PS domain for receiving PS and specifically SMS.
6. The PS-only features shall not affect PS services or SMS and shall work whether the UE has an assigned Mobile Subscriber Integrated Services Digital Network-Number (MSISDN) or not.
3GPP TS 22.368 V11.3.0, Service requirements for Machine-Type Communications (MTC), Stage 1 (Release 11) (September 2011) specifies requirements for PS-only operation, and 3GPP Tdoc S2-114349, PS Domain Only: Inhibiting CS Domain except for SMS over SGs, proposed a solution to fulfill the six architecture requirements of Tdoc S2-115461. 3GPP Tdoc S2-114349 was presented at the 3GPP TSG SA WG2 Meeting #87, Jeju Island, Korea, Oct. 10-14, 2011. In particular, new reject cause values are provided in Attach Accept messages that indicate to a UE receiving such a message that it shall not use the 2G and 3G Circuit Switched (CS) domains and that it is permitted to attempt combined updates in a Long Term Evolution (LTE), or E-UTRAN, network. In addition, an InsertSubscriberData response from a Home Location Register (HLR) to a MSC includes an accessRestrictionData information element that restricts the UE to LTE-only CS-domain SMS (which is to say, the UE is not allowed SMS over a 2G or 30-network CS domain).
The techniques described in Tdoc S2-115461 and Tdoc S2-114349 can still cause a UE to attempt registration over the CS domain, which can lead to rejection of the registration attempt and therefore to increased network signaling. In addition, the techniques described above do not work unless a UE's subscription is changed to a PS-only subscription, i.e., a network operator cannot simply switch on SMS over the PS domain in its 2G/3G network and offload its CS domain for any existing subscriptions.